A Supplement to: NIGMS (R35 GM126935)--EPR Spectroscopic Studies of Membrane Proteins In Response to: PA-18-591, NIGMS Program of Administrative Supplements for Equipment Funds are requested from NIGMS to upgrade the console on our pulse EPR spectrometer that will improve the quality of EPR data collected, allow the instrument to be serviceable in the future, and enable us to better answer important KCNE1/Q1 biological questions. Abstract: Currently, we have limited structural information on membrane proteins. The Lorigan lab is interested in developing new biophysical methods to probe the structural and dynamic properties of integral membrane proteins using state-of-the-art pulsed Electron Paramagnetic Resonance (EPR) spectroscopic techniques and membrane solubilizing polymers. The overall objective is to study membrane proteins with EPR in a lipid bilayer as opposed to a micelle or detergent because it more closely mimics a cell membrane. Several proteins have been shown to not function or fold up correctly in a micelle when compared to a lipid bilayer. This is challenging because it is more difficult to express, purify, and conduct biophysical spectroscopic measurements on membrane proteins when compared to micelle or globular systems. My expertise in membrane protein EPR coupled with the powerful pulsed EPR instrumentation (DEER and ESEEM) in my lab that can measure long range distances has attracted several significant collaborators with important biological problems. The major biological focus of the lab is on membrane protein channels that are directly related to heart disease. KCNQ1 (Q1) is a biologically significant voltage gated potassium channel found in the heart that is modulated by the membrane protein KCNE1 (E1). KCNQ1/KCNE1 interactions slow down the activation kinetics of KCNQ1 required for proper channel and heart function. Hereditary mutations in Q1/E1 can cause Long-QT syndrome, atrial fibrillation, sudden infant death syndrome, cardiac arrhythmias, and congenital deafness. Q1 is a membrane protein with six transmembrane (TMD) helices, the first four TMDs form the voltage sensor domain Q1-VSD (S1-S4), linked to the pore domain (S5- S6) by the S4-S5 linker and the cytosolic N and C-terminal domains. Several studies on VSD channels suggested that the VSD maintains the structural conformation and functional properties in a similar manner to the full-length channel. However, recent solution NMR structural and modeling studies of the VSD of Q1 in detergent micelles indicated overall structural similarities between Q1-VSD and VSDs from other ion channels. However, differences were also observed in the sequential location of helices in Q1-VSD and other VSDs. The three-dimensional structure of KCNQ1 or the E1/Q1 complex has not been determined. Furthermore, the structural nature of the binding interaction/mechanism of E1 with Q1 is poorly understood and has only been investigated indirectly with biochemical binding and cross-linking assays. We are currently applying state-of-the-art EPR techniques to directly probe the structural and dynamic properties of Q1 and the E1/Q1 complex. Transformative biophysical techniques will be developed to study the structural and dynamic properties of membrane proteins. These state-of-the-art pulsed EPR spectroscopic techniques will move the field forward by dramatically increasing sensitivity and distance measurements for all membrane protein systems.